Signal translating device



Oct. 30, 1945. H. H. BRUDERLIN SIGNAL TRANSLATING- DEVICE Filed June 21, 1941 3 Sheets-Sheet l AT TOKNEY' Oct. 30, 1945. H. H. BRUDERLIN 2,333,115

SIGNAL TRANSLATING DEVICE Filed June 21, 1941 3 Sheets-Sheet 2 INVENTOIQ' w k 24m fl T y A m m Oct. 30, 1945. v H. H. BRUDERLIN 2,388,116

SIGNAL TRANSLATING DEVICE Filed June 21, 1941 3 Sheets-Sheet S Patented Oct. 30, 1945 UNITED STATES PATENT OFFICE 2.888.110 SIGNAL 'rasns'm'mio nsvrcs Henry 11. Brnderlin, Hermosa Beach, can.

Application June :1, 1941, Serial No. seam Claims. (Cl. ire-mar) This invention relates to signal translating devices, and more particularly to an improved device for quality recording or reproducing of sound by the aid of a vibratory stylus.

In recording or reproducing sound on a record member, a stylu is placed in contact with a record groove. In recording, the stylus is vibrated to cause the recording point of the stylus to vibrate laterally or vertically, to form a lateral or a hilland-dale record, respectively. The stylus point may actually out the record, or may operate as a pressure em tool. Vibrations may be imparted to the stylus electromagnetically, the signaling impulses determining the amplitude and frequency of the vibrations. Conversely, in reproducing such a record, a stylus is vibrated by the undulations in the record. The vibrations thus produced are caused to induce corresponding signaling impulses in a circuit governing sound reproduction by a loud speaker. i

In either case, the mounting of the stylus is quite important. It is essential that the stylus follow the impulses as accurately as possible, without introducing undesired extraneous vibrations. Ordinarily a resilient restraint is placed upon the stylus, tending to return the stylus to a neutral or inactive position, to ensure that the forces influencing the stylus are suitably rendered effective to vibrate the stylus in substantially accurate conformity with these forces. Restraints of this general character, such as a resilient rubber mounting. or a spring mounting, or a combination of the two, have been heretofore proposed and used. However, it is diflicult by means usually employed to secure the highly desirable cooperative restraint without the introduction of disturbing damping or resonant effects.

It is one of the objects of this invention to im-- prove the mounting of such a stylus and to minimize these disturbing characteristics.

It is another object of this invention to provide a stylus mounting that is simple and inexpensive to construct, and one that produces a natural frequency of the vibratory system that is substantially ineffective in interfering with the accuracy of the recording or reproduction.

It is still another object of this inventirTr'i to provide a mounting that is protected against injury even upon rough usage, such as dropping of the head incorporating the stylus mount.

The stylus mounting is furthermore so arranged that only a light spring pressure may be utilised to hold the stylus point in operative position against the record groove; thereby reducing groove wear, as well as stylus wear. This feature. coupled with the inherently small inertia of the vibratory system, ensures that even very low amplitude signals may be accurately recorded or reproduced, resulting in a very sensitive unit.

can be constructed of extremely small mass. Its: moment of inertia may be thus reduced to a value of the order of one'one-hundredth of that of the conventional pick-ups or recorders. In the relatively massive conventionalreproducing devices, the inertia of the moving parts resulted in rapid wear, due to the accelerating reactions between the groove and the stylus. Also. in the prior art devices, due to their weight and shape, the moving mass was capable of internal resonant vibration in several modes and at several frequencies which strongly and adversely affected their frequency characteristics. These effects caused additional record wear at those frequencies.

It is accordingly still a further oblect of the present invention to provide an extremely small vibratory armature which is incapable of internal resonance at any frequency in the useful range; and to mount the armature in such manner that the assembly of the armature and its mounting as installed in the pick-up or recorder will ordinarily have only one possible type of extraneous resonant vibration, which is outside of or above the useful frequency range.

These and further objects of the invention will become apparent in the following description of preferred embodiments thereof illustrated in the drawings, in which:

Fig. 1 is a vertical longitudinal sectional view of the invention.

Figs. 2 and 3 are transverse sectional views taken respectively along lines 1-! and 3-3 of Fig. 1.

Fig. 4 is a bottom plan view, partly broken away, of the device shown in Fig. 1.

Fig. 5 is a pictorial view of some of the parts of the device shown in Fig. 1, illustrated in separated form.

Fig. 6 is an enlarged fragmentary sectional view of the device, shown in use in connection witha record.

record grooves on its surface. the, grooves is stylus point 2.

, Fig-Its the device.

Fig. 8 isaside view partly in section, of amodian enlarged fragmentary end view of fied found the device.

illustrating a modified form of parts of the invention.

Fig. 13 a cross-sectional view taken along line Il-II of Fig. 12.

Fig. 14 is a view corresponding to Fig. 12, of a further modified form of parts of the invention.

Fig. 15 is a cross-sectional line I5I5 of Fig. 14.

Fig. 16 is a view corresponding to Fig. 12 of a still further modified form of parts of the invenview taken along tion.

Fig. 17 illustrates the mode device illustrated in Fig. 16. p

The device illustrated in Figs. 1 to 7 inclusive may be used either for recording or for reproducing sound inconjunction with a usual record. Record I may be of disk form with a series of Cooperating with The illustrated lateral. recording,

of operation of the record grooves correspond to f asdistinguished from a hill-and-dale record.

The-"stylus point 2 of the device of Figs. 1 to 7 is. for either the recording or reproducing of sound intendd tovibrate in a direction transverse to "the record grooves. rather than his vertical direction along the depth of the. groove as in the hill-and-dale'system. The stylus point 2, however, is supported so as to be flexible in the vertical direction. It is to be understood that tapetype or other record forms may be used in place of the usual disk record. Also, it is to be understood that by suitable variation in the supporting structure for the stylus, the device of the invention may be readily converted for hill-anddale recording and reproducing. I

Stylus point 2 may be made integral with a stylus body 3, or may otherwise be firmly attached thereto, the stylus body 3 and point 2 forming a stylus structure. The stylus is shown supported upon a member 4 capable of vibration in a manner to'be hereinafter described. For reproducing purposes, the vibrations are transmitted to stylus 3 by the action of the lateral record in the record grooves upon stylus point 2. For recording purposes the vibrations are transmitted electromagnetically to the stylus 3 in accordance with the sound impulses to be recorded, whereupon the stylus point 2 cuts or embosses the surface of record I in conformity with the impulses. Since the function of recording as distinguished from reproduction ingeneral corresponds to a reversal of forces operating upon the member 4, the following description of the invention device will be in connection with its use as a reproducer. Operation of the device as a recorder will be defined hereinafter.

Member 4 is made of magnetic material so that it may operate as an' armature in an air gap 5 between pole pieces 6 and I. Assuming that the structure comprising the point 2, stylus body 3 and the armature 4 can swing about a point 8 '(Fig. 7) spaced from the polar axis 9, it is seen that movement of the stylus in a clockwise direction due to the conformation of the lateral record, will reduce the magnetic reluctance between t in Fig. 1.

armature 4 and pole piece I; simultaneously increasing the magnetic reluctance between armature 4 and pole piece 6. Conversely, a vibration of the stylus in a clockwise direction about point 8 will increase the magnetic reluctance between the armature 4 and the pole piece I, simultaneously reducing the magnetic reluctance between armature 4 and the pole piece 8. Accordingly, the vibrations of the armature 4 imparted by the lateral record I are effective in altering the reluctances of mag etic paths.

These variations in the magnetic path reluctances vary the lines of force passing through the core of pick-up coil I0, inducing an electrometive force therein. The magnetic circuit for coil I0 will be described in detail hereinafter. Coil I0 is provided with leads II and I2 which may be connected to an appropriate amplifier and loud speaker system, or other suitable ound reproducer.

Coil I0 is shown disposed over a core I3, illustrated as made up of a series of laminations. Core I3 is shown with its left hand surface in contact with a permanent magnet I4, having its polar faces 2| and 22 in contact with the extensions I5 and I6 of pole pieces Ii and I. Accordingly. if pole piece 6 forms a north pole, then pole piece 1 forms a corresponding south pole, as indicated in Figs. 2 and 7. A magnetic member I! is provided for completing the magnetic circuit through armature 4'. Magnetic-member I'I abuts the lower surface of the leg I8 of the core I3. Member I1 extends toward the left to form a face I9 cooperating with the rear surface 20 of the armature 4. Surfaces I9 and 20 approach quite closely together.

Assuming that the armature 4 is in its neutral or central position, the resultant flux in core I3 is neutralized. This is apparent when it is realized that core I3 abuts the central or neutral zone of magnet I4. Magnet I4 may be assumed as being made up of two magnets, abutting at the region where the core contacts it; this being indicated by dot-and-dash line I00 of Fig. 2.v Flux from the north end corresponding to face 2| can flow through extension I5, armature 4, member I1, and through core I3 toward the left as viewed This flux passes back to the region adjacent line I00, corresponding to a south pole of this half of magnet I4. Similarly, flux from the north end of the right hand portion of magnet I4, corresponding to the region adjacent line I00, flows through core I3 in the direction such as to neutralize the flux in core I3 that is set up by tle left hand half of magnet I4 as viewed in Fig.

Assuming now that the magnetic reluctance from armature 4 to the south pole 1 is reduced by movement of the armature 4 in a counterclockwise direction as illustrated in Fig. 7, then flux may pass through the core I3 in a magnetic circuit including pole I. This circuit includes the south polar region of the left hand half of magnet I4, adjacent line I00 (Fig. 2), through core I3 in the direction of arrow 23 in Fig. 1, member I7, armature 4, polar extension 1, back to the south pole of magnet I4. A magnetic flux through this path will accordingly pass through core I3 in the direction of arrow 23. The flux set up in this direction is quite strong, because the reluctance of the circuit is reduced by the approach of armature 4 toward polar projection 1.

Another magnetic circuit of greater reluctance is simultaneously effective through which magof this electromotive force pathmay be traced as follows: from the north.

polar end of the left hand halfof magnet i4 (Fig. 2), pole piece 8. armature 4. member il,

leg Moore l8.b'acktothenorthpolarregion correspondingtolineiN...

As armaturelisvibratedaboutaxistthedb rection ofthe flux through the core lllpasses through successive reversals. This is due to fact that armature l alternatively approaches pole pieces I and I, setting up resultant opposite variations in magnetic. reluctance between the armature and these pole pieces. These changes -of flux throughcore ll induce an electromotive force in coil II. The "amplitude and frequency are in conformity with therecordgrooves. issupporte The manner in which armature l I for vibratory movement of this character will now be described. ,There is provided a flat spring member 24, preferably made of non-magnetic spring metaLsuch as phosphor bronze or spring brass. The upper surface of armature l is attached tothe free end of wring II, as by soldering or the like. The opposite end of spring is is clamped between a non-magnetic I supporting member 2! and magnetic member II or is preferably attached in member il as by soldering. A flat head screw "passes through member i1, and is threaded into member II. This single screw mounting allows the armature-spring assembly to be quickly replaced when necessary.

The conflguration of member I! is shown most clearlyin Fig. 5. It is provided with downwardly extending ears orlugs 21 on opposite sides of its rear end. between which the rear end of member il is disposed. Member II is also provided with a rear slot II within which the lower end of leg II is accommodated. It is also provided with a front slot II contiguous with arms it and ll between which armature 4 may extend. Lugs 21 serve to center member i1. Therefore in con Junction with screw 28, armature 4 is constrained to be accurately positioned in the gap between the pole pieces l and I. These pieces may be soldered to arms I. and ii. Alternatively member 2| may be eliminated and its functions accomplished by a plastic member of similar or of difl'erent shape. In some constructions, spring 24 may be made of magnetic material, obviating the necessity of using member II.

To provide a suitable casing for the entire head, a rear supporting member I! made of insulation material may beprovided. Support 32 in con- Junction with a enacting housing a, encloses the device except for a comparatively narrow slot in the bottom wall of the casing. ,Armature 4 may extend through slots 34. Permanent magnet il may be disposed on an inwardly turned lip OI formed in the left hand wall of casing a. Fastening screws 30, (Figs. 1 and 4) may be provided for holding the housing If in position with respect to the member 32. Furthermore, in order to hold core is securely against magnet ll, use may be made of a leaf spring 31 acting on the rear end of the core i3 and anchored. as with a rivet fl, to member 32.

An important feature of this construction is the character of spring 24 supporting armature I. The support provided is such as to permit armature 4 to vibrate in the air gap betweenpole .pieceslandlbytwistingofspringll aboutits longitudinal axis. Spring 2| may be aptly termed a torsional spring. 'It is about the longitudinal axis of spring 24 that the lateral vibrations of the stylus occur. Furthermore, spring 1| is capable of being flexed in a vertical direction.- The operating pressure on thestylus is suillcient to cause the flexure of spring 2 upwards to the position indicated in Fig. I. This pressure may be as low as one-half ounce, with attendant satisfactory operation. This is only a fractionof pressure ordinarily utilized on conventional magnetic pick-up units, which generally require approximately three ounces of pressure. Armature l is purposely made rather deep: so that even.

upon the flexure of spring 24 the armature extends fully across the magnetic fleld between pole pieces land I. Furthermore, the free end of spring 24 ordinarily, but not necessarily, serves as the sole support for the armature.

Spring It may aptLv be referred to as a cantilever leaf spring It has three degrees of deflection; one in torsion about its longitudinalaxis; one in flexure in a direction'perpendicular to the lane or the spring; and one in flexure in the plane of the spring. The torsional stiffness of spring 2! must be suiiicient to prevent the armature 4 from sticking to the poles if it is displaced that far, but not still enough to prevent the stylus from freely following the vibrations in the record. The vertical flexure stiffness of the spring must be sufllcient so that with the proper operating pressure applied to the stylus the spring will not deflect excessively. The spring must be sullciently flexible in the vertical direction so that if excessive pressure is applied to the styh's it will recede between the pole pieces due to deflection of the spring so that neither'the stylus on 40 other parts will be iniured because of excessive stylus pressure.

The lateral stiflness of spring 24 must be sumcient so that under operating conditions; that is, with the stylus applied to the record, the lateral resonant frequency of the vibratory system comprising the armature and spring will be above the useful operating range of the pick-up. This is the only type of extraneous vibration which will'occur in the operating mechanism of this pick-up. The torsion axis of spring I4 is transverse to the polar axis 0, but spaced a considerable distance above it. In this way the amplitude of movement of armature 4 between pole pieces 0 and l is nearly the same as the vibratory movement of the tip 2.

The entire vibrating system of the invention device is extremely light. The natural resonant frequency of the supporting system may accordingly be readily designed to lie beyond the useful audio frequency range of reproduction. Extraneous or disturbing oscillations are therefore largely avoided or suppressed. The resonant frequency of the combined stylus 2, I, armature l and spring suspension 24 may in practice be constructed to lie between 6000 cycles per second to 10,000 cycles per second, or even higher. Thus, the natural tendency of the overall frequency characteristics in reproduction by records to taper oil may be directly compensated at the higher frequency end by this resonant characteristic. In other words, by placing the resonant frequency of the aforementioned vibratory system at the higher range, the frequency deterioration normally inherent in such systems is boosted so that the overall characteristic of reproduction may be virtually uniform over a far greater frequency range than heretofore practicable. I have found that a mechanical reproducer constructed in accordance with the inventionhas'uniform or substantially flat frequency response characteristics ment of the stylus point upwardly with respect to the pole pieces! and 1. Therefore the maximum spring force acting upon stylus point 2 by flexureof spring 24 is quite small. The torsional twisting of spring 24 along its longitudinal axis permits the point2 to ride over the walls of the record grooves in the event that the device is forcibly moved transversely of the record. Stylus point 2 readily rides over the walls of the groove by slanting about the axis of the inadvertent dropping of the head on the record slope. This slope is such as to reduce any variation in the air gap between these two surfaces irrespective of the transverse flexure of the spring 24. Spring 24 in Fig. 6 is shown flexed to about its normal extent while the device is in operation.

The manner in which the invention device may be utilized for recording will be understood by those skilled in-the art, marized. In such instances, the recording impulses are electrically introduced to coil ID. The magnetic flux through core I3 is thereupon caused to vary in accordance with the impulses to be recorded. The magnetomotive force supplied by coil I causes the central magnetic portion (including core l3, member I 1, and armature 4) to be magnetized with an alternating or pulsating magnetic flux in correspondence with changes in the current fed to coil l0. This magnetic portion reacts magnetically with the pole pieces of the permanent magnet. Armature 4 will therealternateiy between pole pieces Iand l'as the induced polarity of the armature 4 changes, controlling the action of stylus point 2 in cutting the record pattern.

A modified form of the invention is illustrated in Figs. 8 to 11. Armature 39 in this case is similar to the one already described. It operates in the air gapbetween pole pieces 40, 4|. These pole pieces are formed as extensions of the horizontal legs 42, 43 of shoes 44, 45, netic material. The vertical legs of shoes 44, 45 are placed in contact with the polar ends 46 and 41 of a permanent horseshoe magnet 48. Torface of the cylindrical core 5| for coil 52. the axis-of the coil 52 is transverse to the axis of spring arm 49. Magnetic member 50 serves the same function as magnetic member ll of the form first described. Torsion spring 49 by the aid of screw 55 passing through magnet member 50, being threaded into core 5|.

A non-magnetic supporting member 53 is utilized to support the structure. Horizontal legs spring 24. Furthermore,

and will now be summade of mag-- n, u of the shoes 44, u may be attached to the forward end of supporting member 53, as by the aid of the fastening means 54. This support 53, shown most clearly in Fig. 10, has a central depression 59 through which, the bottom of core 5| passes. The supporting member 53 is held in place, as by being clamped between spring member 49 and the bottom of coil 52, or by soldering. welding, or a force lit. 7 I

To ensure that magnetic member 50 will not be displaced from thecentral position illustrated in. Fig. 11, member 53 may have inwardly extendinto the upper operation described in connection with the form illustrated in Fig. l. The magnetic circuits through core 5i may be traced from north pole piece 40, armature 39, magnetic member 50, core 5|, permanent magnet creased magnetic flux upwardly through core 5| whenever armature 39 is tilted toward the north pole. When armature 39 istilted in the opposite direction a strong magnetic flux passes downwardly through core 5! in the following manner: from the north pole of horseshoe magnet '48, downwardly through core 5|, magnetic member 50, armature 39, south pole 4|, shoe 45, and back to the permanent magnet.

The sole support for the stylus BI, 92 may be torsion spring 49, as hereinbei'ore, although additional supports might be used. This torsion spring can twist about its longitudinal axis to is possible to secure the viding asloping portion 19 which slopes upwardly from the point of anchorage of the spring 68 be held in place aasane toward the armature H. At the free end of the portion 6| the spring III drops downwardly for attachment to the top surface of the armature H.

The axis of oscillation of the vibrating struc-' ture may be represented by point 12, illustrated in Fig, 1'7. The movement of armature II in the air gap is made more nearly to correspond with the lateral movement of the stylus point It. The volume of reproduction is thereby increased, and in recording greater forces are available to act on the record groove.

The forms described above incorporate only a single coil. It is well known that a structure of this type is susceptible to extraneous magnetic fields. In cases where the recorder or pick-up is to be used in locations with strong extraneous magnetic fields, the coil and core structure may take the form of a U-shaped core and double coil in accordance with the hum-bucking prin- 'ciple now extensively used in the construction of transformers. The coils may of course be wound with any electrical impedance desired.

Although I have described and illustrated preferred exempliflcations which my invention may assume in practice, it is to be understood that modifications may be made therein without aiiecting the principle and scope thereof as defined in the appended claims.

What is claimed is:

1. A sound translating device for lateral recording comprising means forming a pair of opposed magnetic poles and a central return path portion, an armature disposed between and having surfaces cooperative with said poles and portion, a stylus carried by said armature, a leaf spring serving as the principalsupport for said armature and having a torsion axis spaced at a substantial distance from the axis of said poles, the opposed surfaces of said portion and armature being similarly sloped transversely to reduce air gap variations therebetween corresponding to tlexures of said spring. 7

2. In a sound translating device for lateral recording, means forming a pair of spaced magnetic poles of opposite polarity, an armature disposed in the space between the'poles, a stylus carried by said armat coil means, a core for said coil means having one end in the magnetic circuit to both poles,-means cooperating with said armature to complete the magnetic circuit through the armature and the core by way of either pole, and means providing for said armature to move pivotally with respect to said poles to reduce the magnetic reluctance for a circuit,

through one pole and to increase the magnetic reluctance for a circuit through the other pole in correspondence with lateral displacements of said stylus comprising a torsion spring having an axis of torsion spaced a substantial distance from the pole axis and forming the sole support for the armature.

3. A sound translating device for sound recording comprising means forming a pair of spaced magnetic poles of opposite polarity, an armature disposed in the space between the poles, a stylus carried by said armature, coil means. a core for said coil means having one end in the magnetic circuit to both poles, means cooperating with said armature to complete the magn tic circuit through said armature and said core by way of either pole, and means providing for permitting said armature to move pivotally with respect to said poles to reduce the magnetic reluctance ior a circuit through one pole and to increase the magnetic reluctance for a circuit through the other pole in correspondence with lateral displacements of said stylus comprising a torsion spring having an axis of torsion spaced a substantial distance from the pole axis, and forming the principal support for the armature, said spring having freedom of torsional twist as well as in a direction transverse to the Spring at the place where the armature is supported.

4. In a sound translating device for lateral recording, means forming a pair of spaced magnetic poles of opposite polarity, an armature disposed in the space between the poles, a stylus carried by said armature, coil means, a core for said coil means having one end in the magnetic circuit to both poles, magnetic means cooperating with said armature to complete the magnetic circuit through said armature and said core by way of either pole, and means providing for said armature to reduce the magnetic reluctance for a circuit through one pole and to increase the magnetic reluctance for a circuitthrough the other pole in correspondence with lateral displacements of said stylus comprising a torsion spring having an axis of torsion spaced a substantial distance from the pole axis and forming the principal support for the armature, said spring axis being transverse to the pole axis.

5. A sound translating device comprising means forming a pair of spaced magnetic poles of opposite polarity, an armature disposed in the space between said poles, coil means, a core: for

said coil means having one end in the magnetic circuit to both poles. magnetic means cooperating with said armature to complete the magnetic circuit through said armature and said core by Y way of either pole, and means providing for said armature to reduce the magnetic reluctance for a. circuit through one pole and to increase the magnetic reluctance for a circuit through the other pole comprising a torsion spring having an axis of torsion spaced a substantial distance from the pole axis and forming the principal support for said armature, and supported by the aid of said magnetic means.

6. A sound translating device of the character described comprising means forming a pair of spaced magnetic poles of opposite polarity, an armature disposed in the space between the poles, coil means, a core for said coil means having one end in the magnetic circuit to both poles, a stylus carried by said armature, magnetic means cooperating with said armature to complete the magnetic circuit through said armature and said core by way of either pole. and means Providing for said armature to reduce the magnetic reluctance for a circuit through one pole and to increasethe magnetic reluctance for a circuit through the other pole comprising a torsion spring having an axis of torsion spaced a substantial distance from the pole axis and forming the sole support for the armature.

HENRY H. BRUDERLIN. 

